Conventionally, techniques for monitoring a road surface abnormality, such as a level difference in a road surface, a crack in the ground, and the like, are known. For example, there is a system in which a driver of an automobile gives a notification about accident information including an accident occurrence location, and the like, to an information collection center using a mobile phone with a global positioning system (GPS) that positions a location of a road surface, or using a car navigation device with a communication function. The information collection center aggregates accident information, and the like, which have been collected from respective drivers, and estimates an accurate accident occurrence location on the basis of a result of aggregation.
Furthermore, in recent years, wireless terminal devices, such as a smart phone, and the like, which include an acceleration sensor therein, have been widely used, and therefore, a system that diagnoses a road surface condition on the basis of a measurement result of an acceleration sensor is also known.
Related techniques are disclosed in, for example, Japanese Laid-open Patent Publication No. 2005-157410 and Japanese Laid-open Patent Publication No. 2007-193475.
In accurately positioning a location of a road surface, a wireless terminal device often uses GPS, and it is desired to reduce an operation time of GPS and thereby reduce the power consumption of GPS because the power consumption used by GPS for performing measurement operation is large.